This invention relates to a suspension system for heavy duty trucks, and more particularly, the invention relates to a suspension system having a drive axle assembly.
Heavy duty trucks typically utilize a trailing arm suspension system having one suspension member or arm. In the case of drive axles, the drive axle is supported by a lower suspension member that is pivotally connected to the frame. The drive axle includes an input shaft that has a U-joint on the end for connection to a driveshaft. The input shaft and U-joint of the drive axle assembly has what is commonly referred to as a pinion angle, which is the angle of the centerline of the input shaft relative to a horizontal plane. The drive axle is typically rigidly connected to the suspension member and an air spring is arranged between the suspension member and the frame. As the suspension moves up and down during operation of the heavy duty vehicle, the pinion angle changes. Excessive pinion angle changes, which may occur during normal vehicle operation, may cause increased wear and undesirable operation of the U-joint.
Suspensions have been proposed for use with non-drive axle assemblies which have a lower arm and an upper arm spaced from the lower arm interconnecting the frame and the axle assembly. However, in the case of a drive axle assembly the upper or lower arm must be adjusted to obtain a desired pinion angle. Accordingly, what is needed is a suspension system for a drive axle assembly that permits the adjustment of the pinion angle and which maintains the pinion angle during suspension movement in the course of normal heavy duty vehicle operation.
The present invention provides a suspension for a heavy duty vehicle that includes a frame. A lower linkage is supported by the frame at a first pivotal connection. A drive axle assembly is supported by a lower linkage at a second pivotal connection. The drive axle assembly includes an input shaft defining a pinion angle. An upper linkage interconnects the drive axle assembly and the frame at third and fourth pivotal connections, respectively. The upper linkage includes an adjustment member, such as a turnbuckle, for modifying the length of the upper linkage to obtain a predetermined pinion angle. In this manner, the pinion angle may be adjusted upon assembly of the suspension system. Furthermore, by permitting the drive axle assembly to pivotally move relative to the linkages, the pinion angle may be maintained during suspension movement.
Accordingly, the above invention provides a suspension system which permits adjustment and maintains pinion angle.